Ball valve seal for high temperature operation

ABSTRACT

A ball valve seal comprising a seal ring of yieldable material and of rectangular cross-section, though with one inner corner removed leaving a conical sealing surface. A seat ring assembly almost completely contains the seal ring, engaging both readial and both cylindrical surfaces to inhibit cold flow of the seal material, with just the conical surface exposed. A groove around the outer cylindrical surface of the seal ring provides space for thermal expansion relative to the seat ring. A back seal ring, which seals around the seat ring, has an internal conical surface that engages a complementary surface on the seat ring assembly whereby hoop tension provides a spring force under axial load.

United States Patent 1 1 Murphy et al. 1 1 Mar. 27, 1973 s41 BALL VALVESEAL FOR HIGH 3,487,823 1 1970 Tarter et al ..25l/367 x R T RE OPERATION3,497,l78 2 1970 Priese ..251 31s x 3,6l7,025 11 1971 Gerbic ..251 315 x1 Invemmf Francis F 'P Y Greensb-ufg; 3,620,243 11/1971 Zatopek .251/315x William L. Kane, Trafford, both of Primary Examiner-Samuel Scott [73]Assignee: Walworth Company, Bala Cynwyd, AtwmeyMelvin Stidham Pa. [57]ABSTRACT [22] F1led: Mar. 22, 1971 A b n l I, 1 f Id bl a va ve sea commm a sea rm 0 1e a e [21] App! 126348 material and of rectangularross-sectiori thoigh with one inner corner removed leaving a conicalsealing [52] US. Cl ..251/315 surface. A seat ring assembly almostcompletely con- [51] Int. Cl ..F16k 5/06 ains he eal ring, engaging bothreadial and both [58] Field of Search ..25l/3.l5,3l6, 175, 359, 360cylindrical surfaces to inhibit cold flow of the seal material, withjust the conical surface exposed. A [56] References Cited groove aroundthe outer cylindrical surface of the seal ring provides space forthermal expansion relative to v UNITED STATES PATENTS the seat ring. Aback seal ring, which sealsaround the 3,211,421 10 1965 Johnson, Jr. eta1..... .251 315 seat ring, has an internal mical Surface that engages3,497,176 2 1970 Priese .....2s1/31s x a 9mpl9m9ntary Surface on the aring assembly 3,131,906 5/1964 King ..25l/3l.5 X whereby hoop tensionprovides a spring force under 3,416,558 12/1968 Works.; ..25l'/3l5 Xaxial load. 3,439,897 4/1969 Priese et al. .....25 l[3l5 X 3,460,8028/l969 Co'lby et al. ..25l/3 l 5 X 10 Claims, 3 Drawing Figures Patentedarch 27, 1973 3,722,859

2 Sheets-Sheet l 24 l v 26 44 IV/ I 48 l T";

l ENTORS FRANC .MU Y

Y WILUAM L. KA

A j H ATTORNEY Patented March 27, 1973 3,722,859

2 Sheets-Sheet 2 INVENTORS FRANCIS E. MURPHY WILLIAM L. KANE ATTORNEYBALL VALVE SEAL FOR HIGH TEMPERATURE OPERATION BACKGROUND OF THEINVENTION This application relates to a ball valve seal for hightemperature operation, and, more particularly, to a ball valve with aseal ring of yieldable material which is resistent to high temperaturesand/or high pressures.

Valves designed for installation in lines conducting fluids at hightemperature, e.g., steam, frequently employ metal to metal seals, thoughin many instances for bubble tight sealing, it is highly desirable touse seals of resilient materials. However, many resilient materials,such as elastomers, are incapable of withstanding high temperatures inthe order of 200 to 500 Fahrenheit. Certain plastic materials arecapable of withstanding high temperatures, but those that aresusceptible to cold flow under pressure, may become distorted underpressure and rendered totally ineffective for sealing purposes.

. OBJECTS OF THE INVENTION It is an object of this invention to providea seal ring assembly including a plastic seal ring which is almostentirely contained within a rigid seat ring assembly.

It is a further object of this invention to provide-a forces the outercylindrical surface of the back seal ring rigidly contained plastic sealring with a groove around seat ring assembly with a back seal thatfunctions also as a yieldable biasing member.

Other objects and advantages of this invention will become apparent fromthe description to follow when read in conjunction with the accompanyingdrawings.

BRIEF SUMMARY OF THE INVENTION In carrying out this invention, a ballvalve is provided with seat ring assemblies, each assembly being made upof two-piece rigid holder rings, which together form a recess for a sealring of yieldable plastic material. The inner holder ring forms theradial recess bottom surface and the cylindrical inner recess wall. Theleading edge of the inner recess wall is machined as a conical orspherical surface to form a secondary fire-safe" metal seat. The outerholder ring comprises the cylindrical outer wall, with an inward radialextension forming a front retainer. The resilient seal member isbasically of rectangular cross-section with an inner corner removed,forming an inner conical sealing surface for engagement with the ball.Both of the cylindrical surfaces and both of the planar radial surfacesare engaged by the rigid holder ring assembly so that the seal member isalmost entirely contained to inhibit distortion under cold flow. Agroove is formed around the outer periphery of the seal member to leavea space within the recess for thermal expansion. The seat ring into firmsealing engagement with the cylindrical surrounding holder ring recessforming a positive seal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section view of aball valve embodying features of this invention;

FIG. 2 is an enlarged partial section view of one of the seat ringassemblies of FIG. 1; and

FIG. 3 is an exploded isometric view of the seat ring assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularlyto FIG. 1, the ball valve 10 of the inventionincludes a valve bodysection 12 having an integral flange 14 to which is secured a bodyclosure 16 by anyv suitable means such as the bolts 18. Inlet and outletflow passages 20 and 22 are formed in the body 12 and the body closure16, and both sections are provided with flanges 24 and 26 or othersuitable means for connection into a pipeline (not shown).

The ball valve 10 has a floating ball 28 rotatably supported on seatrings 30 to be described in greater detail. The ball may be rotatedthrough between open and closed positions by means of a valve stem 32,which is rotatably carried in the valve body. A driving tang 34 at thelower end of the stem, extends into a complementary slot 36 at the topof the ball 28 to impart rotation to the ball. The stem may be rotatedby any suitable means such as a wrench (not shown) gripping the flats 38at the upper end of the stem. Suitable packing 39 is provided to preventleakage around the stem.

The seat ring assembly 30 (FIG. 2) is mounted in a recess 40 formed inthe valve body and comprises an inner holder ring 42 and an outer holderring 44, together containing a seal member 46 of yieldable material. Theseal member may be formed of a suitable plastic such as a glassreinforced polytetrafluoroethylene sold under the trademark Teflon. Aback seal ring 48 of suitable material, such as Teflon, having a conicalinner surface 50 merging into a cylindrical surface 52 is carried oncomplementary conical and cylindrical surfaces 54 and 56 on the innerholder ring. The back seal ring 48 slides in a counterbore portion 58 ofthe recess 40, whereby the seat ring assembly is free to slide underfluid pressure asserted directly or through the ball. The back seal ring48 seals between the conical surface 54 of the inner holder ring andboth the back wall 60 and the cylindrical wall 58 of the counter-bore.In addition, because of the complementary conical surfaces 50 and 54,axial forces against the seat ring assembly and back seal place the backseal ring 48 under hoop tension to supplement the resilience inherent inthe material and produce greater spring force.

The rigid inner holder ring 42 has a radial leading planar surface 62that forms the bottom of the recess for the plastic seal ring 46, and anannular extension with a cylindrical outer surface 64 that forms a sidewall of the recess. The leading edge of this annular extension ismachined at an angle parallel in cross-section to a tangent of the ball28, to provide a secondary firesafe seat 78 in the event the main sealring 46 is destroyed. The outer seat ring 44 has a cylindrical innersurface 66 forming another side wall of the recess and a radial inwardextension 68 forming a partial outer recess wall.

As shown, the yieldable plastic seal member 46' is of generallyrectangular cross-section with the inner corner removed forming agenerally conical sealing surface 46a for engagement with the ball 28.Hence, both of the radial planar surfaces and both of the cylindricalsurfaces of the seal member are embraced by the rigid seat ringassembly; Because the plastic seal ring is almost completely contained,cold flow of the plastic material is greatly inhibited. At the sametime, thermal expansion of the seal member relative to the rigid seatring assembly is enabled by virtue of a V-groove 70 which is cut aroundthe periphery of the seal member. The cross sectional area of the sealmember relative to that of the groove is calculated to insure that thevolume of the groove is sufficient to permit and accommodate thermalexpansion of the seal member relative to the seat ring assembly, takinginto consideration the coefficient of thermal expansion of the resilientmaterial, the maximum operating temperature for which the valve isdesigned and the maximum seal ring volume to be tolerated. The finaldimensions and the orientation of the groove 70 are determined byconsideration of the structural strength and increased resilience underaxial forces.

The inner seat ring is provided with a V-shaped radial extension 72which snaps into a complementary V- groove 74 which is formed in theinner surface of the outer seat ring 44. A trailing portion of the outerseat ring inner surface is cut away to form a slightly conical cammingsurface 76 which is forced outward by the conical surface 72 of theinner seat ring, allowing them to snap together in firm interlockingengagement.

Under pressure, the ball 28 will tend to move downstream to push thedownstream seat ring assembly 30 against the back seal 48, providing afirm downstream seal. At the same time, the upstream seat ring is biasedin the downstream direction under the force of the back seal, tending tomaintain an upstream seal with the ball. Line pressure behind the seatring assembly 30 forces the back seal 48 into'firm sealing engagementbetween the stepped recess 58 and the seat ring assembly so that itfunctions both as a seal and as a spring.

While this invention has been described in conjunction with a preferredembodiment thereof, it is obvious that modifications and changes thereinmay be made by those skilled in the art without departing from thespirit and scope of this invention.

What is claimed is:

1. A ball valve seat ring assembly comprising:

an inner holder ring,

a generally radial leading surface and an annular extension on saidinner seat ring,

an outer holder ring secured around said inner holder ring, and

an internal cylindrical surface on said outer holder ring intersectingat the trailing end thereof with said leading surface,

an inward radial extension at the forward end of said outer holder ring,and

a seal member of a yieldable material, carried on said holder rings,generally radial trailing and forward surfaces and inner and outercylindrical surfaces on said seal member engagable by said leadingsurface, said inward extension, said annular extension and said internalcylindrical surface, respectively,

said inner and outer holder rings being secured together by interlockingengagement of a V-shaped radial extension around said inner holder ring,and

-a V-groove around said internal cylindrical surface.

2. The seat ring assembly defined by claim 1 including:

a generally conical surface on said seal member intersecting said innercylindrical and forward radial surfaces to engage a valve ball closuremember.

3. The seat ring assembly defined by claim 1 wherein:

the trailing portion of the outer holder ring is reduced in thicknessand tapered outward rearward from said V-groove so that said trailingportion may be cammed outward by said radial extension to snap saidextension into and out of said V- groove.

4. The seat ring assembly defined by claim 1 wherein: the leading edgeof the annular extension on said inner seat ring is formed on a taper.

5. The seat ring assembly defined by claim 1 includmg:

an external conical surface on said inner holder ring tapering inwardrearward of said leading surface,

a back seal ring of yieldable material carried on said inner holderring, and

complementary conical and cylindrical surfaces on said seal ringslidable on said external conical and cylindrical surfaces of said innerholder ring.

6. The seat ring assembly defined by claim 5 includsaid back seal ringextends rearward of said inner holder ring and is adapted for sealingengagement with the bottom wall of a valve body recess.

7. A valve structure comprising? a valve body with flow passagestherethrough,

a closure member mounted in said body and having a v flow blockingsurface thereon movable into and out of alignment with one of said flowpassages,

a recess in said valve body around said one flow passage, and

a seat ring assembly slidably received in said recess,

an external conical surface on said seat ring assembly tapering inwardtoward the back thereof,

a trailing external cylindrical surface extending rearward from saidexternal conical surface,

a back seal ring of yieldable material, and

complementary conical and cylindrical surfaces on said back seal ringslidable on said external conical and cylindrical surfaces on said seatring assembly.

8. The valve structure defined in claim 7 including:

a generally radial leading surface and an annular ex tension on saidinner seat ring, an outer holder ring secured around .said inner holderring, and an internal cylindrical surface on said outer holder ringintersecting at the trailing end thereof with said leading surface,

an inward radial extension at the forward end of said outer holder ring,and

a seal ring of a yieldable material, having a greater coefficient ofthermal expansion than that of the inner and outer holder rings carriedon said holder rings,

generally radial trailing and forward surfaces and inner and outercylindrical surfaces on said seal ring engagable by said leadingsurface, said inward extension, said annular extension and said internalcylindrical surface, respectively, to be substantially confined thereby,

a groove around said seal ring of an area in cross-section sufficient toaccommodate greater thermal expansion of said seal member relative tosaid inner and outer holder rings.

1. A ball valve seat ring assembly comprising: an inner holder ring, agenerally radial leading surface and an annular extension on said innerseat ring, an outer holder ring secured around said inner holder ring,and an internal cylindrical surface on said outer holder ringintersecting at the trailing end thereof with said leading surface, aninward radial extension at the forward end of said outer holder ring,and a seal member of a yieldable material, carried on said holder rings,generally radial trailing and forward surfaces and inner and outercylindrical surfaces on said seal member engagable by said leadingsurface, said inward extension, said annular extension and said internalcylindrical surface, respectively, said inner and outer holder ringsbeing secured together by interlocking engagement of a V-shaped radialextension around said inner holder ring, and a V-groove around saidinternal cylindrical surface.
 2. The Seat ring assembly defined by claim1 including: a generally conical surface on said seal memberintersecting said inner cylindrical and forward radial surfaces toengage a valve ball closure member.
 3. The seat ring assembly defined byclaim 1 wherein: the trailing portion of the outer holder ring isreduced in thickness and tapered outward rearward from said V-groove sothat said trailing portion may be cammed outward by said radialextension to snap said extension into and out of said V-groove.
 4. Theseat ring assembly defined by claim 1 wherein: the leading edge of theannular extension on said inner seat ring is formed on a taper.
 5. Theseat ring assembly defined by claim 1 including: an external conicalsurface on said inner holder ring tapering inward rearward of saidleading surface, a back seal ring of yieldable material carried on saidinner holder ring, and complementary conical and cylindrical surfaces onsaid seal ring slidable on said external conical and cylindricalsurfaces of said inner holder ring.
 6. The seat ring assembly defined byclaim 5 including: said back seal ring extends rearward of said innerholder ring and is adapted for sealing engagement with the bottom wallof a valve body recess.
 7. A valve structure comprising: a valve bodywith flow passages therethrough, a closure member mounted in said bodyand having a flow blocking surface thereon movable into and out ofalignment with one of said flow passages, a recess in said valve bodyaround said one flow passage, and a seat ring assembly slidably receivedin said recess, an external conical surface on said seat ring assemblytapering inward toward the back thereof, a trailing external cylindricalsurface extending rearward from said external conical surface, a backseal ring of yieldable material, and complementary conical andcylindrical surfaces on said back seal ring slidable on said externalconical and cylindrical surfaces on said seat ring assembly.
 8. Thevalve structure defined in claim 7 including: a generally radial bottomwall in said valve body recess, said back seal ring being in sealingengagement with said recess bottom wall.
 9. The valve structure definedby claim 8 including: a cylindrical wall in said valve body recess, anda complementary outer cylindrical surface on said back seal ring insliding engagement with said cylindrical wall.
 10. A ball valve seatring assembly for high temperature operation comprising: an inner holderring, a generally radial leading surface and an annular extension onsaid inner seat ring, an outer holder ring secured around said innerholder ring, and an internal cylindrical surface on said outer holderring intersecting at the trailing end thereof with said leading surface,an inward radial extension at the forward end of said outer holder ring,and a seal ring of a yieldable material, having a greater coefficient ofthermal expansion than that of the inner and outer holder rings carriedon said holder rings, generally radial trailing and forward surfaces andinner and outer cylindrical surfaces on said seal ring engagable by saidleading surface, said inward extension, said annular extension and saidinternal cylindrical surface, respectively, to be substantially confinedthereby, a groove around said seal ring of an area in cross-sectionsufficient to accommodate greater thermal expansion of said seal memberrelative to said inner and outer holder rings.